A number of previously issued patents describe batteries which include at least one metal layer having a peripheral lip which is sealed to at least one other component of the battery as part of the peripheral sealing system for the battery. U.S. Pat. No. 3,775,188, for example, describes a process of indenting pockets in the metal layers, the indented pockets being situated inside the peripheral sealing system and over the electrodes of the battery.
We have discovered that when these peripheral lips in the metal layers are left as essentially plane surfaces there is a tendency for concentrated wrinkles to develop at one or more locations along the lip. These wrinkles, which we believe are probably produced by accumulations of stresses developed during sealing, are undesirable inasmuch as they may provide leakage paths through what is intended to be a moisture-tight peripheral sealing system and/or they may result in unwanted electrical paths in the battery.
We also believe that stresses may occur in that portion of the metal layer situated inside the peripheral sealing system, which stresses may tend to produce wrinkles in that portion of the metal layer. These wrinkles are potentially undesirable and should also be avoided.
Our invention is aimed at achieving a battery of the type described above which is free from these wrinkles.